Design, Photography, & Fashion

Photography 101: What Is a Zoom Lens? Learn About the Purpose of Zoom Lenses, Plus Different Types of Zoom Lenses

Written by MasterClass

Aug 8, 2019 • 4 min read

When selecting a lens for your mirrorless or DSLR camera, you have two broad categories of lens options. The first is a prime lens, which offers a single focal length that cannot be adjusted. The other category is that of zoom lenses, which allows a range of focal lengths that can be changed with manual adjustment.

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What Is a Zoom Lens?

A zoom lens is an SLR or DSLR lens that offers a different focal length for the photographer to select from. A zoom lens can be manually adjusted by a user to create focused images throughout a wide range of distances from one’s photographic subject, from very close-up to very far away. This is different to a prime lens, which is a lens with a fixed focal length.

What Is the History of Zoom Lenses?

Precursors to today’s zoom lenses date back to the 1830s, when they were components within optical telescopes. The zoom lens began to be used in cameras when Clile C. Allen invented a zoom lense for motion pictures in 1902. It wasn’t until the 1920’s, however, when zoom lenses became more widely used in cinema, like in the 1927 film It, starring Clara Bow. Film legends like Orson Welles and Alfred Hitchcock both popularized the use of the zoom lens in film, which prompted further development and enhancement of zoom lens technology both for cinema and for photography.

Zoom lenses remain widely used on today’s mirrorless and DSLR cameras, like those manufactured by Nikon, Canon, Sony, and others. They can improve image quality in both full light environments (set to a low aperture) and low light environments (set at or near maximum aperture). The most popular zoom lenses are manufactured by Nikon, Canon, and Tamron.

What Are the Advantages of Using a Zoom Lens?

A zoom lens offers many advantages to both professional and amateur photographers alike. Most of these relate to the adjustment of focal length, but there are a number of other advantages.

  • Versatility. Unlike a prime lens, a zoom lens offers multiple focal lengths in one package.
  • Artistic possibilities. A zoom lens allows magnification of images and the ability to crop out unwanted subject matter.
  • Visual resolution. If you’re able to spring for a top-notch zoom lens, you may find one with sharpness that’s highly comparable to a prime lens.
  • Ability to change focal length on the go. Adjusting focal length allows you to keep shooting without having to attach and detach lenses from your camera body.
  • Preferable to post-photography digital zooming. An optical zoom lens will allow you to take photographs of different focal lengths while maintaining the maximum resolution allowed by your camera’s lens. Emulating this featuring using digital zoom cannot match the quality offered by a photograph taken with an optical zoom lens.

What Are the Different Types of Zoom Lenses?

Some of the most common types of zoom lenses include:

  • A parfocal lens, which maintains focus across all of its possible focal lengths. (This is sometimes called a “true zoom” lens.)
  • A varifocal lens, which loses focus when its focal length is changed. These lenses require an additional user step of refocusing once a new focal length is selected. The vast majority of zoom lenses sold to consumers are varifocal lenses.
  • A telescopic lens or a superzoom lens may provide a larger range of focal lengths than a standard parfocal or varifocal zoom.
  • A wide-angle zoom lens allows a user to adjust focal lengths while also enjoying a wider horizontal image than would be possible with a traditional zoom lens.

What Is the Difference Between Optical and Digital Zoom?

The primary difference between optical and digital zoom is that optical zoom involves a physical mechanism that changes the focal length of the lens. Digital zoom has no physical component; it is a software manipulation.

  • When one measures optical zoom, one is measuring the increase in the lens’s focal length. The further the lens is from the camera’s image sensor, the greater the amount of zoom.
  • Digital zoom is less easily measured. One digital camera manufacturer’s metrics for digital zoom may be different from that of another manufacturer. What digital zoom effectively does is crop an existing image and magnify whatever is in the center of that image. The physical lens itself remains at a fixed focal length; in other words, it functions as a prime lens. For this reason, digital zoom on your camera or phone is in fact no different from zooming in and cropping a photograph on your home PC.

Digital zoom necessitates the removal of pixels from a larger image, which degrades the overall quality of the photo. If digital zoom needs to be used, keep in mind that it works best on extremely high-resolution photos; if the resolution is low to begin with, digitally zooming in will quickly render a photo grainy and visually undesirable.

What Is the Difference Between a Zoom Lens and a Telephoto Lens?

Some amateur photographers use the term “telephoto lens” as a synonym for “zoom lens.” In truth, these two lenses are not identical.

  • A telephoto lens has a long reach—traditionally this means a focal length of 60mm or more—but it does not necessarily need to slide through a zoom range of varying focal lengths. This means that some telephoto lenses are actually prime lenses, though there are many telephoto zoom lenses available on the market.
  • By contrast, a zoom lens is defined by being able to slide through many focal lengths, but there are zoom camera lenses that don’t magnify enough to be considered “telephoto.”

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